It's been one of my major pet peeves on both Android and iOS: the total and utter lack of consistency. Applications - whether first party or third party - all seem to live on islands, doing their own thing, making their own design choices regarding basic UI interactions, developing their own non-standard buttons and controls. Consistency died five years ago, and nobody seems to care but me.

I agree good UIs are fewer and further between because of the lack of consistency. I submit, however, that the cause may be generational in nature.

First, you should note that "different" can cause confusion which can lead to frustration, and perhaps, eventually anger. Consistency is a mechanism that minimizes unnecessary differences, and hence, confusion and frustration, and perhaps even anger. That said....

As we age we become more and more creatures of habit. When confronted with new devices [and interfaces] we tend to expect to trigger "common" functionality in ways consistent with our prior experiences. Unnecessary differences confuse and frustrate us.

What is interesting to me is that the younger generation seems to adapt to newness better than most old folk, perhaps because they are not encumbered with a lot of prior experiences. And because today's younger designers do not feel the confusion and frustration, consistency is not a major consideration in their designs.

But don't give up. Have hope. The consistency pendulum will swing back as this younger generation gains experience, gets confused, and feels the frustration. Our challenge is to live long enough to see the resurgence. One can only hope.